Many industrial applications require the use of high-speed turbo machinery. For example, in the production of industrial gases such as oxygen, nitrogen, argon, and the like via liquefaction and fractional distillation of air, turbo expanders are used to reduce pressure of the air and/or the individual gaseous components.
Compliant foil gas bearings have been applied successfully to a wide range of high speed rotating machinery. These gas foil type bearings are especially attractive to turbo expanders because they eliminate the lube oil system, simplify the seal gas system, simplify the control system, offer lower frictional power loss, and provide greater flexibility of machine installation.
Such devices are shown in U.S. Pat. Nos. 3,893,733, 4,133,585, 4,167,295, 4,262,975, and 4,300,806. In addition to the compliant hydrodynamic bearings of the prior art, attempts were made to use foil bearings in conjunction with a magnetic field such as shown in U.S. Pat. No. 4,167,295.
The compliant foil gas bearings suffer from low capacity and low damping capability when compared to more conventional oil film type bearings.
As shown by the prior art, an attempt was made to increase damping and load capacity of compliant foil gas bearings using a tapered land configuration which is simulated by using a varying bump foil stiffness technique such as shown in the '975 Patent. The '806 Patent shows a dual bump foil configuration that was another attempt to increase the load capacity and damping capability of the bump foil compliant gas bearing.